ZCZC MIATCDEP1 ALL TTAA00 KNHC DDHHMM TROPICAL STORM PRISCILLA DISCUSSION NUMBER 1 NWS NATIONAL HURRICANE CENTER MIAMI FL EP162013 200 AM PDT MON OCT 14 2013 SATELLITE AND MICROWAVE DATA SHOW THAT THE AREA OF LOW PRESSURE LOCATED WELL SOUTHWEST OF THE SOUTHERN TIP OF THE BAJA CALIFORNIA PENINSULA HAS ACQUIRED ENOUGH ORGANIZED DEEP CONVECTION TO BE CLASSIFIED AS A TROPICAL CYCLONE. IN ADDITION...A COUPLE OF ASCAT PASSES AND SHIP OBSERVATIONS FROM THE RESEARCH VESSEL MELVILLE... INDICATE THAT THE SYSTEM HAS MAXIMUM WINDS OF 35 KT. AS A RESULT...ADVISORIES ARE BEING INITIATED ON TROPICAL STORM PRISCILLA...THE SIXTEENTH TROPICAL STORM OF THE SEASON IN THE EASTERN NORTH PACIFIC BASIN. OVERNIGHT SATELLITE FIXES SHOW THAT THE CYCLONE HAS BEEN MOVING NORTH-NORTHEASTWARD AT A FASTER RATE THAN WAS OBSERVED DURING THE DAY YESTERDAY...HOWEVER THE INITIAL MOTION OF 015/10 KT IS A BIT MORE UNCERTAIN THAN NORMAL. PRISCILLA SHOULD MOVE NORTH- NORTHEASTWARD TO NORTHWARD DURING THE NEXT DAY OR TWO AS IT MOVES AROUND THE WESTERN PORTION OF A MID-LEVEL RIDGE OVER MEXICO. IN A COUPLE OF DAYS...THE RIDGE IS FORECAST TO WEAKEN WHICH SHOULD CAUSE THE CYCLONE TO SLOW DOWN AND TURN NORTHWESTWARD. AS PRISCILLA WEAKENS AND BECOMES A SHALLOWER CYCLONE LATER IN THE PERIOD...IT IS EXPECTED TO SLOW DOWN WITHIN AN AREA OF WEAK LOW-LEVEL STEERING FLOW WELL WEST-SOUTHWEST OF THE BAJA CALIFORNIA PENINSULA. PRISCILLA IS A SHEARED TROPICAL CYCLONE WITH THE CENTER LOCATED NEAR THE NORTHEASTERN EDGE OF THE CONVECTIVE MASS. EAST-NORTHEASTERLY SHEAR IS FORECAST TO CONTINUE OVER THE CYCLONE DURING THE NEXT 24 HOURS...BUT SOME SLIGHT STRENGTHENING IS POSSIBLE DURING THAT TIME. ALTHOUGH THE VERTICAL SHEAR OVER PRISCILLA IS FORECAST TO DECREASE IN 36 TO 48 HOURS...THE CYCLONE WILL BE APPROACHING COOL WATERS AND A MORE STABLE AIRMASS. THIS SHOULD RESULT IN GRADUAL WEAKENING BY 48 HOURS...AND PRISCILLA IS EXPECTED TO DEGENERATE INTO A REMNANT LOW WITHIN 3 TO 4 DAYS. FORECAST POSITIONS AND MAX WINDS INIT 14/0900Z 14.3N 115.7W 35 KT 40 MPH 12H 14/1800Z 15.8N 115.2W 40 KT 45 MPH 24H 15/0600Z 17.0N 115.1W 45 KT 50 MPH 36H 15/1800Z 18.1N 115.1W 45 KT 50 MPH 48H 16/0600Z 19.2N 115.7W 40 KT 45 MPH 72H 17/0600Z 20.5N 116.5W 30 KT 35 MPH 96H 18/0600Z 21.0N 117.5W 25 KT 30 MPH...POST-TROP/REMNT LOW 120H 19/0600Z 21.0N 118.0W 20 KT 25 MPH...POST-TROP/REMNT LOW $$ FORECASTER BROWN NNNN